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The hertz (symbol Hz) is the SI unit of frequency. It is named in honour of the German physicist Heinrich Rudolf Hertz who made some important contributions to science in the field of electromagnetism.

One hertz simply means "one per second"; 100 Hz means "one hundred per second", and so on. The unit may be applied to any periodic event – for example, a clock might be said to tick at 1 Hz.

The old name for the unit was cycles per second (cps), and this term is sometimes seen, along with its related multiples (kilocycles, megacycles, and so forth) in writing from before the second world war.

SI Multiples

1 kilohertz kHz 103 Hz 1 000 Hz
1 megahertz MHz 106 Hz 1 000 000 Hz
1 gigahertz GHz 109 Hz 1 000 000 000 Hz
1 terahertz THz 1012 Hz 1 000 000 000 000 Hz
1 petahertz PHz 1015 Hz 1 000 000 000 000 000 Hz
1 exahertz EHz 1018 Hz 1 000 000 000 000 000 000 Hz


Hertz is also the name of a car rental company. See The Hertz Corporation.

Last updated: 02-08-2005 16:36:23
Last updated: 03-18-2005 11:16:12